When HGH is referred to by the color of the vial caps it's usually generic growth hormone made by various labs in China. There are not more than a handful certified labs, capable of producing real 191 amino acid sequence somatropin. The necessary lab equipment to produce the HGH is a multi million dollar investment - unreachable for a "bathtub" steroid lab. Furthermore, the required know how includes genetic manipulation of E.Coli bacteria which then secrete the human version of growth hormone. When somatropin is harvested, the bacteria have to be filtered out, which is a very difficult undertaking.
So which color of HGH tops to buy?
Trying to distinguish the generic HGH by the color of the caps is like trying to judge people by the color of their jackets. The color of the caps can freely and easily be switched from batch to batch. This results in endless bodybuilding forum discussions where people report good and bad results from blue tops, green tops, red tops, yellow tops, etc.
If buying generic HGH, the only way to really make sure that what you are about to use will not bring damage to your body is to lab test it beforehand. There are two types of tests you can do. Either a complete lab analysis of the substance (done by a lab capable of performing the test) or using your body as a guinea pig, injecting a full vial and performing a HGH/IGF serum test. See the "Real of fake HGH? How to test it?" page for more info.
Beware of the 192 amino acid sequence GH (Somatrem)
It is less difficult (and cheaper) to produce the 192 amino acid mimic, which is technically not really somatropin. The difference is 1 additional methionyl amino acid attached to the sequence. While generally the effects of using the 192 aa somatrem are similar to somatropin treatment, the different molecule can bring about serious health issues. It is possible that the body's immune system detects the somatrem as foreign and attacks it. Because the foreign 192 and body's own 191 amino acid hormones are very similar, it can lead to the body attacking it's own HGH as well. This autoimmune condition would leave a person without growth hormone - which the body needs for regeneration, metabolism and various important functions.
Beware of the Low purity HGH containing bacterial residue
It is very improbable for a small lab to be capable of extracting the somatropin without bacterial residue in it. Injecting a low purity HGH it often produces painful red welts around injection spot - which is a good indication that the body's immune system has detected the bacterial residue as foreign and is mounting an attack. Potentially this can also lead to the body rejecting it's own naturally produced growth hormone which then leads to serious health issues.
History of colors of the HGH tops
Before the existence of generic HGH labs in China, the yellow tops were used by Jintropin (GeneScience Pharmaceuticals), blue tops were used by Hypertropin (Neogenica Bioscience) and green tops were used for Igtropin (IGF-1 long R3).
In 2007, both Jintropin and Hypertropin switched to using green color caps. Igtropin (IGF-1) was renamed to Revitropin and the color of caps was changed to blue. A few years later Revitropin was renamed to IGF3 and has since been using the red caps.
Brand name embedded in the cap
Some labs have periodically used the name of their brand printed on the vial caps. This has lately been abandoned by most because it can easily be copied and also limits the company's ability to distribute their products under OEM brand names.